1. Field of the Invention
The present invention relates to a skin covered foamed plastic seat and, more particularly, to such a seat incorporating holes at desired positions, and to a process of manufacturing the seat.
2. Description of the Background Art
Car seat cushions and seat backs have been made of a pad member covered by a skin cover. The pad member and the skin cover used to be manufactured separately and combined together later, but it has become the practice to manufacture a skin covered pad member altogether by making the foamed plastic inside the skin cover placed over a molding surface, so that the process of combining at a later time may be omitted.
One of the most common problems encountered in such a process of manufacturing a skin covered pad member is the leakage of the liquid foam resin which will become a pad member onto the front surface of the skin cover.
In general, the skin cover comprises an air permeable front surface skin and a backing material called wadding which is not air permeable. This wadding may be effective enough to prevent the leakage of the liquid foam resin, but for a skin covered pad member such as that to be used for a rear seat cushion which is required to have holes for inserting the seat belts, the problem of the leakage of the liquid foam resin cannot be prevented by such wadding, so the effective method to prevent such leakage in such a case has not been known conventionally.
Normally, the required holes on the skin covered pad member are manufactured by using a mold with bossings corresponding to the holes to be made, but when the skin cover is placed over the mold, there is usually a small space between these bossings and the edges of the skin cover surrounding the bossings, so that when the liquid foam resin is poured into the mold, the leakage of the liquid foam resin through such a space between the bossings and the edges of the skin cover occurs, and the leaked liquid foam resin will be foamed on the front surface of the skin cover which has to be removed afterwards. This leaked foam resin after the foaming of the liquid foam resin is not easily removable, so that the leakage of the liquid foam resin can severely affect the manufacturing efficiency.
Even when the bossings are made to fit with the edges of the skin cover tightly at the beginning of the manufacturing process, the force due to the expansion of the liquid foam resin in the foaming process which will tend to pull the skin cover away from the bossings can create a space between the bossings and the edges of the skin cover, so that the leakage cannot be prevented.